and, yes, no question that the 20 years in the nfl was the majority. but i think the issue is, i believe very strongly, kids under the age of 14 should be playing flag football not tackle football. not taking the shots to the head. but from the ages of 14 on up, if individuals understand the risks and they have passion for the sport, i wouldn't say don't play it, but i would say play it wisely and play it with proper technique and that means not hitting with your head. >> see, if i'm a parent that still really concerns me because a 14-year-old might not be ready to understand the consequences of playing football. and how do you explain to that kid what might happen, and more importantly, how can that child protect himself? >> well, there is no absolute way of protecting yourself playing tackle football. in the act of tackling, that's when most of the concussions happen because that's when most of the head contact happens. so, tackle football has inherent risks, unquestionably. and if you're going to play it, you have to understand that concussions can